Flexible flat cable (FFC), featuring a thin thickness and excellent flexibility, is used in a variety of uses for its high degree of freedom in implementation into electronic devices. It is widely used, for example, in a steering roll connector (SRC) which is a component of an airbag system in an automobile, in a folding part of a folding mobile telephone, in movable parts for digital cameras, printer heads, and the like, and in wiring and the like of movable parts in disk related devices such as a hard disk drive (HDD), digital versatile disc (DVD), compact disk (CD), and the like.
Note that rolled copper foil has been widely used conventionally in conductor parts for flexible flat cables.
Here, a rectangular conductor is disclosed in Japanese Unexamined Patent Application Publication No. 2009-048819 with a conductor composed of pure copper with a Cu concentration of 99.9% or more and an electrical conductivity of 95% or higher, the tensile strength being in a range greater than or equal to 350 MPa and less than or equal to 400 MPa. The rectangular conductor is used in automobiles, or the like, that can reach high temperature environments of 85° C. or higher, and achieves price reduction and maintains conductor strength.
Further, in Japanese Unexamined Patent Application Publication No. 2010-150578, a rolled copper foil after a final cold rolling process but prior to recrystallization annealing is disclosed wherein a diffraction peak exists due to a grain group exhibiting 4-fold symmetry residing in at least 90±5° each of β angles in a range where an α angle is within 40° to 50° as a positive pole figure result of {220} Cu surface diffraction of copper crystals by x-ray diffraction pole figure measurement as a reference for a rolled surface, and moreover, a diffraction peak exists due to a different grain group exhibiting 4-fold symmetry residing in 90±10° each of the β angles. Japanese Unexamined Patent Application Publication No. 2010-150578 provides a rolled copper foil having excellent flexing characteristics in response to the need for higher flexing characteristics relative to flexible wiring members such as flexible printed wiring boards and the like.
In Japanese Unexamined Patent Application Publication No. 2001-262296 a method of manufacturing a copper foil produced by subjecting an ingot of oxygen-free copper to hot rolling, then repeating cold rolling and annealing, and finishing with cold rolling to a thickness of 0.0050 mm or less is disclosed, wherein a cube texture is extremely developed by sequentially performing (1) cold rolling to 90% or more of the working ratio, (2) recrystallization annealing in a furnace at a temperature between 150 and 250° C. for 1 to 10 hours, or recrystallization annealing in a furnace at a temperature between 500° C. and 800° C. for 5 to 60 seconds, and (3) cold rolling to 5 to 40% of working ratio. Japanese Unexamined Patent Application Publication No. 2001-262296 also provides a copper foil favorable for use as a flexible wiring member such as a flexible printed circuit board and the like.